Freezing tray



Nov. 13, 1951 F. w. SAMPSON FREEZING TRAY 2 SHEETS.--SHEET 1 Filed Feb. 14, 1948 /end MJ'm aun J'J W Mahdi/kg for table use.

Patented Nov.13, 1951 4 FREEZING TRAY Frederick W. Sampson, Dayton, Ohio, minor to General Motors Corporation, Detroit, a corporation of Delaware Mich.,

Application February 14, 1948, Serial No. 8,352 2 claims. (Cl. 62-10) This invention relates to freezing trays especially suchas are adapted for use in domestic refrigerators to produce ice blocks of suitable size -Heretofore there have been many patents issued on various forms of freezing trays having as the overall purpose the harvesting of theice cubes therefrom without any melting being required to aid in such harvesting. In some prior devices it has been alleged that the ice cubes are automatically released by the expansion which occurs when water freezes into ice. However so far as known all such alleged devices possess inherent serious defects and hence have found no commercial use. I

Now the object of this invention is to provide a freezing tray whose ice blocks will consistently be automatically loosened either fully or very materially, by the freezing of the water into ice without the necessity of maintaining other than normal freezing conditions, i. e. conditions within the range normally available in household refrigerators.

Another object is to provide such a freezing tray from which the ice blocks may be readily freed from both the pan and the grid by a simple manual flexing thereof without removing the grid from the pan. Such flexing operation is very useful when the automatic loosening of the ice blocks is not sufficiently complete to permit immediate removal of the ice blocks with the fingers or ice tongs when the freezing tray is taken from its freezing compartment.

Another object is to provide such a freezing tray which does not require filling to a very precise water level in order to insure that the grid will be automatically lifted upwardly from the pan by the freezing of the water in some of the ice block compartments.

Another object is to provide such a freezing tray wherein the freezing of the final portions to freeze of some of the ice blocks force said iceblocks to move laterally outwardly from a central grid wall and thereby aid in the loosening of said ice blocks.

Further objects and advantages of thepresent invention will be apparent from the following description reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. l is a plan view of the removable grid inserted into the container pan in freezing position therein. No water or ice is shown in the grid or pan in Figs. 1 and 2.

2 t Fig. 2 is a section on line 22 of Fig. 1.

Figs. 3 to 8 are partial views illustrati Several stages in the progressive freezing of the water into ice. Figs. 3 and 4 show the flrst stage illustrated.

Fig. 3 is similar to the left portion of Fig. 2, and I illustrates a thin layer of ice formed on top of the water contents and a relatively thick layer of ice wherever the water directly contacts the pan surfaces. Fig. 3 is taken on line 3-3 of Fig. 4. Fig. 4 is a partial plan view of Fig. 3, and shows in dotted lines the outline of the bottom area of the still unfrozen water.

Figs. 5 and 6 roughly illustrate a later stage in the progressive freezing.

Fig. 5 shows the central portion of the pan andgrid, and illustrates how the freezing progresses chiefly by a continued thickening of the layers of ice contacting the pan surfaces. Fig. 5 is taken on line 5-5 of Fig. 6.

Fig. 6 is a partial plan view of Fig. 5 and shows in dotted lines the outline of only the bottom areas of the still unfrozen water.

Figs. '7 and 8 show the third stage of freezing illustrated.

Fig. 7 is similar to the right portion of Fig. 2 and shows the freezing of the ice blocks nearing completion. Fig. 7 is taken on line 'l-'l of Fig. 8.

Fig. 8 is a partial plan view of Fig. 'l and shows in dotted lines the outline of the still unfrozen water in the several ice block compartments shown.

Similar reference characters refer to similar parts throughout the drawings.

Reference numeral I0 designates a flexible metal container pan which has such flexibility that it can be easily flexed by hand by twisting its two ends in opposite directions. Preferably pan i0 is a one-piece sheet metal stamping of aluminum or other good heat-conducting metal. Pan l0 has a flat bottom ll, slightly outwardly inclined side walls i2, and outwardly inclined end walls [3. A downwardly turned margin [4 forms a stiffening flange extending around the upper edges of walls l2 and Hi. When pan i0 is set upon a flat supporting surface and downward pressure applied to the upper edges of any two diagonally opposite corners, as by an operator pressing on said corners with the balls of his two hands, the entire pan will be given a limited torsional twist due to the substantial overhang of said corners beyond the flat bottom portion II which rests upon the supporting surface. This overhang at the two ends of pan l0 may be greatly increased without materially changing the shape and size of the endmost ice block by providing the slightly inclined bottom areas I! on the otherwise flat bottom H, as best shown in Fig. 2. These bottom areas ii are inclined upwardly prelcrably at about or degrees from the line i6. This increased overhang materially facilitates a limited torsional twisting of both the pan and the inserted grid therein by the operator pressing down on any two diagonally opposed corners as described above.

The removable grid preferably has its partition walls integrally molded from a slightly flexible plastic material to which a water film does not adhere. The plastic partition walls preferably are molded of such material and thickness that they will not stretch or bulge out materially at local areas under the expanding force of the ice blocks as they freeze. The confining partition walls should be sufficiently rigid and strong as to cause the expansion in volume upon freezing of the water trapped in the lower compartments to lift the entire grid upwardly relative to the pan, as later described herein. However the grid as a unit should be sufliciently flexible to be readily given a twisting distortion by pressing down upon any two diagonally opposite corners with the two hands of the operator. Of course thicker sections of partition walls would permit using a more flexible plastic material, but this adds materially to the weight and cost of the grid and also reduces the space left for the ice. I found polystyrene to be a very suitable plastic material when the partition walls are made only one sixteenth inch thick. Of course some other flexible plastic materials having suitable physical characteristics of rigidity and strength may be used. Commercial polyethylene now available is an example of a plastic material which is not very suitable for making this particular grid because of its tendency to stretch and bulge out at local areas in the partition walls as the trapped water turns into ice, whereby the automatic forced lifting of the grid relative to the pan is materially reduced.

Grid 20 comprises a longitudinal main wall 2i and a series of preferably inclined transverse or cross walls 22 integral therewith and projecting laterally on opposite sides thereof. Cross walls 22 preferably extend close to the side walls l2 of .pan I0. All the lower ice block compartments thus formed have top cover walls 23, and the four end compartments 26 have top cover walls 24. These cover walls 23 and 24 are integrally molded with the adjacent main wall 2i and cross walls 22 and extend laterally into contact with or reasonably close to the pan walls i2 and I3 when the grid is inserted into its freezing position in pan l0 (see Figs. 1 and 2). Thus all the lower compartments 25 and 26 are substantially enclosed on all six sides thereof when the grid is properly inserted in pan ill, but of course water can leak past the cracks 21 between the ends of cross walls 22 and the side walls l2 of the pan sumciently to cause the water to reach the same level in all compartments when the tray is filled. Also the cracks 28 between the outer ends of cover walls 23 and 24 and the pan walls l2 are not water-tight. The endmost cover walls 24 preferably have small integral flanges 20 thereon where said cover walls 24 meet the end walls [3 of pan [0, however the cracks 29 between said flanges 30 and the inclined end walls ii of the pan are also not water-tight. These small flanges 50 aid in trapping the water and ice in the four end compartments 26 as expansion takes place upon freezings but their chief function is to render the cover walls 24 more rigid so that they will not flex upwardly too easily under the expanding pressure of the freezing water in said end compartments 24, as herein later described.

The ice block compartments 40 which lie alternately between the lower compartments 26 will be termed the "upper compartments, since they have no cover walls and to some extent overlie compartments 25. Compartments 40 preferably have flat bottom walls 4| which lie flat against the flat portion of pan bottom ii when the grid is in freezing position in the pan as shown in Figs. 1 and 2. These flat bottom walls 4i are in effect a horizontal continuation of the two ad- Jacent cross walls 22 and are molded integrally therewith. Thus bottom walls 4i serve as structural members which provide increased rigidity and strength of the grid as a whole, and aid importantly in flexing the cross walls during the manual twisting of the grid to free the remaining bond of the cubes. Bottom walls 4i preferably terminate at their end edges 42 approximately at the line where the flat bottom Ii of the pan begins to curve upwardly to merge with the pan side walls l2.

In the form illustrated in the drawings, the grid 20 is provided with a projecting handle 49 molded integral with the main wall 2i, cover wall 24 and its end flange 30. Handle 40 provides a convenient means for manually tilting or lifting the grid 20 from the pan at any time. A similar handle may also be provided at the opposite end of the grid if so desired. It will be clear from viewing Figs. 1 and 2 that such grid handles 49 will not interfere with the stacking of several such freezing trays one upon the other within a freezing chamber of a refrigerator, this because the flat handles 49 will be located well beyond the two ends of the bottom of the superposed pan resting immediately upon the flush top edges of grid 20. Hence the stacking one upon the other of trays comprising the pan and grid of this invention requires only a minimum head room in any freezing chamber since there is no waste head room in such a stack.

The operation of this freezing tray will now be described. The tray is filled with water to a level at or reasonably close to the cover walls 23 and 24, which preferably lie about of an inch below the top edge of pan Ill. The water level may vary considerably however. If the water level is higher than the top surfaces of cover walls 23 and 24 the thin layers of ice which form on top of these cover walls may be wasted but this will not prevent good operation of the tray. If the water level is slightly below the bottom surfaces of cover walls 23 and 24 some air will be trapped on the top of the water in the lower compartments 25 and 26 but such trapped air will not prevent good operation because the water in compartments 25 will upon freezing increase in volume about 8.5%, or slightly more than one-twelfth its volume at 32 F. Due to the upwardly tapered shape of the compartments 25 a considerable depth of trapped air at the narrowed top of these compartments would still fall short of being one-twelfth of the volume of said compartments 25, hence the increase in volume of the water upon freezing would still be sufflcient to lift the grid upwardly from the pan.

The filled tray is inserted into a freezing chamber, preferably on a flat metal refrigerated support or shelf. The heat is conducted from the water contents thru the good-heat-conductins walls of pan l0 very much faster than the being quite thin and easily broken.

. Q cold air above the tray takes up heat directly from the water. For this reason when freezing begins the first substantial layers of ice form on the bottom, side, .and end walls of pan ll while perhaps a mere skim of ice forms on the top of the water.

Figs. 3 and 4 illustrate roughly the usual reintive thicknesses of the different layers of ice after freezing has progressed to this first illustrated stage. Here the thickest layers of ice have formed in direct contact with the pan bottom Ii, side walls i2 and end walls It. The next thickest layers of ice have formed immediately above the plastic bottom walls ll of compartments Ill, since the heat flow from the water to the pan bottom It is decreased by the relatively poor heat conductivity of the interposed plastic walls ll. The thinnest layers of ice will be formed on the top surfaces of the water in compartments 25, 28 and 40 these top ice layers Thedotted lines 60 in Fig. 3 outline the trapped volume of still unfrozen water in the lower end compartments 26. The dotted lines II and 52 outline the trapped still unfrozen water in the lower compartments 25. The dotted lines 52 and 54 outline the unfrozen water in the upper compartments 40 wherein this water is not trapped other than by the easily broken top layers of ice. In Figs. 4 and 6 the ice is not shown other than as indicated by the dotted lines 50. 5i and 52 in Fig. 4 and the similar dotted lines ii and 53 in Fig. 6, all of which show the outline of only the bottom surfaces of the still unfrozen water. This showing in Figs. 4 and 6 is thus simplified to avoid confusion of too many overlapping lines in these figures.

Figs. 5 and 6 illustrate roughly the relative thicknesses of the different layers of ice after freezing has progressed to this second illustrated stage. Here the layers of ice which contact the side walls l2 and bottom ll of pan id have roughly doubled in thickness over that shown in Figs. 3 and 4, while the layers of ice at the top surfaces of the water are still relatively thin and easily broken.

Figs. '7 and 8 illustrate the freezing nearing completion, the dotted lines indicating the outlines of the small bodies of water which are the last to freeze in each compartment. In the end compartment 26 the small body of water 80 located furthest from the pan walls will be the last to freeze. In the lower compartments 25 the slightly larger bodies of water Si in contact with the center wall 2| will be the last to freeze. In the upper compartments 40 the still larger bodies of water 62 located in contact with the grid center wall 2| will be last to freeze.

It will now be clear that the substantial ice layers which first form over the contacting surfaces of the bottom ll, l3 of pan ID will trap unfrozen water in all the compartments which have covers thereon, namely the lower compartments 25 and26. This trapped water upon progressivelyfreezing must increase in volume as it changes its state to ice, and in so doing can exert an enormous force to raise the grid 20 relative to pan Ill. It has been found that the grid 20 is forced up fromthe pan ill in a series of intermittent small steps rather than by a slow continuous movement. Due to some slight yielding of the confining walls (whether the bottom or side walls of the pan or the grid walls) under the hydraulic pressure of the trapped water, the pressure builds up and is suddenly relieved whenever it builds up sumclently to break the ice bond holding the water trapped.

- Thus the lifting movementof the grid is intermittent. Water under high pressure will super chill, i. e. so slightly below its normal freezingtemperature of 32 1'. Hence when the 8116 is lifted only very slightly and the ice bond holding the water trapped is broken a film of the W water usually starts to force its way out of confinement between the confining walls and the ad- Jacent ice layers, but since the pressure in the water is simultaneously relieved by the movement of the grid this film of water will very quickly freeze due to its having been super chilled to slightly below 32'F. By this action little or no water escapes entirely from the captive cells, and the grid will again be bonded to the pan in its new slightly raised position. This action may be repeated, say 5 to 10 times, to cause the grid to be lifted upwardly from the pan on a succession of intermittent steps until finally all of the trapped water is frozen. After each lifting movement of the grid the new ice bond which holds the grid down does not reform over as great an area as in the preceding case, hence the grid and ice blocks become successively freer and freer with each lifting cycle. By the time the last porsides l2, and end walls tion of the trapped water freezes there remain only a few relatively small bonded areas which bond the ice blocks in the lower compartments to the grid and pan.

The expanding effect of the trapped water in the lower compartments also materially loosens the ice blocks in the upper compartments 4]. This is done in various ways: (1) the lift of the grid necessarily loosens these ice blocks from the slightly tapered side walls l2 of the span; (2) also the ice blocks in the lower compartments 25 upon freezing push out laterally and spring the sides l2 of the pan outwardly to some extent and so aid in.peeling these sides l2 from all the ice blocks in contact with sides l2; (3) some slight flexing and outward bulging of the central portions of cross walls 22 by the confined water in the lower compartments aids in loosening the ice blocks in the upper compartments 40, since it takes only a very minute flexing movement of said walls 22 to loosen them from the ice blocks on the opposite surfaces thereof. It is to be understood that in some cases where water is trapped and put under pressure by a continued freezing the ice immediately adjacent to the confined water is more or less weak or even mushy and hence will serve as a medium to transmit the hydraulic pressure of the confined water.

It is pointed out that Figs. 3 to 8 inclusive make no attempt to illustrate the small lifting movements of the grid from the pan, or any of the other small movements of the ice blocks relative to the grid walls or the pan, since it is thought any such attempt would be confusin rather than clarifying. But referring particularly to Figs. '3, 5 and 7, it will be clear that in each of the lower compartments 25 and 26 water will be fully trapped by relatively thick strongice layers; that the pressure in said trapped water will be increased as the ice layers continue to thicken; that said pressure exerts a lifting force upon the grid; that said pressure exerts a down force upon the pan bottom which tends to flex said bottom and loosen its frozen bond to its supporting shelf; that said pressure in the trapped water in the lower compartments is also partition wall 2i and hence exerts a lateral force urging the already frozen portions of the ice blocks in silld lower compartments to move laterally outwardly relative to cross walls 22; that such lateral movement will spring both side walls I2 of the pan outwardly and tend to peel said side walls H from all ice blocks in contact therewith; that such outward flexing of side walls IE will also tlex at least the marginal portions of pan bottom H and so tend to peel said bottom ii loose from its frozen bond to its supporting shell! as well as from the pan contents; and that the pressure in the trapped water 60 (see Fig. 7) in the'four endmost ice blocks will exert a force urging these endmost ice blocks outwardly against the opposed inclined end walls I! of the pan. It will also be clear from Figs. 7 and 8 that in the upper compartments 40 the bodies of water 62 will be trapped by a surface layer of ice which in some cases may be quite strong, dependent upon the relative rates of cooling from above and below; that pressure built up in said bodies of water 62 exerts a lateral force on opposite sides of the center wall 2| which reacts to urge the already frozen portions of the ice blocks in said upper compartments to move laterally outward relative to cross walls 22.

All these loosening actions are inherent in the device and are available when needed. It is unnecessary that all of these loosening actions occur in order to permit easy harvesting of the ice blocks as described below. These several automatic loosening actions are affected by the actual freezing conditions in any specific case, such as the air temperature in the freezing chamber, the temperature and heat conductivity of the support upon which the pan rests, the relative heat conductivity of the pan walls and the grid walls, the water lever to which the pan is fllled initially, the relation between the depth of the pan and the dimensions of its bottom surface, the degree of flexibility of the pan walls, the degree of flexibility of the grid walls, and the degree of adhesion of the ice to the various areas.

To harvest the ice blocks, with its frozen contents the tray is easily removed from the freezing chamber and preferably given a slight flexing or twisting by the two hands of the operator to flex both the pan and the grid to loosen whatever remaining small bonded areas between the ice blocks and the grid or pan walls there may be left after the above described automatic loosening. A lengthwise torsional twisting of the entire tray and contents as a unit may be easily done simply by setting the tray upon a suitable support, such as a table and pressing with the balls of the two hands upon any two diagonally opposite corners of the grid and pan. Since the corner areas where such downward force is applied overhang the supporting bottom of the pan a substantial distance at both ends thereof, this will result in a definitely limited torsional twisting of the entire pan and grid. The pan and grid should be designed with sufficient elasticity t permit such limited torsional twisting without taking a permanent set in distorted shape, that is, when the pressure of the two hands is relieved both the pan and grid will spring back to their normal shape shown in Figs. 1 and 2. Such twisting distortion of the pan and grid as a unit will loosen all the individual ice blocks so that they may then be removed individually from the pan and grid. The grid together with the ice blocks loosely retained in the upper compartments 40 may be simply lifted entirely from the an, leaving all the ice blocks in the lower compartments and 26 loose in the pan. Of course the ice blocks may be individually removed in any other desired manner. For instance, only one end of the grid may be raised by means of the small handle 49 to permit the easy removal of the desired number of ice blocks from the upper compartments 0 without disturbing the remaining ice blocks. The grid may then be lowered back into position in the pan and the assembly replaced in the freezing chamber for later use.

The advantages oi twisting of the pan and grid as a unit, that is with the grid in the pan, are as follows: (1) this fully protects the plastic grid from breakage or damage from being twisted too much and over-stressed at any local points therein; (2) this prevents the loosened ice blocks from popping free of the grid onto the floor or other places; (3) when the pan and grid are twisted as a unit as above described it is unnecessary to touch any of the ice blocks with the hands because the plastic covers 24 upon which the balls of the hands ordinarily press overlie the four corner ice blocks and protect them from any contact with the hands of the operator during handling of the tray and contents. Only a slight torsional twisting of the longitudinal center wall 2| of the grid will similarly flex all the inclined cross walls 22 and connecting bottom walls 4i and cover walls 23, since all of said walls 22, 23 and 4| have free outer ends and have their inner ends integrally joined to said center wall 2i. Hence when the grid is even slightly twisted as a whole all partition walls are necessarily urged to flex to some extent. Thus the longitudinal center wall 2| is important in that it serves to transmit a flexing action to all the transverse partition walls. Center wall 2i also provides a stiffening rib which retains the shape and dimensions of the grid thru years of use and so maintains the good fit of the grid to the pan. Center wall 2| also serves to render the grid quite rigid against possible bending in a vertical direction if the freezing of trapped water in all lower compartments 25 happens not to be uniform thruout the length of the grid.

While the embodiment of the present invention constitutes a preferred form it is to be understood that other forms may be adopted all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In combination, an elongated metal freezin pan and a closely fitting grid of molded plastic material removably positioned therein to form with the pan two rows of ice block compartments, said grid comprising: an upright longitudinal main wall extending from end to end of the grid and serving as a continuous relatively rigid backbone for the grid to substantially prevent bending thereof in a vertical direction, a continuous wall integral with and projecting laterally from each side of said longitudinal wall from end to end thereof and shaped to form a series of alternately inverted trapezoidal shaped ice block compartments, said continuous walls forming horizontal fiat top closures for the downwardly opening trapezoidal compartments and flat horizontal bottom walls for the upwardly opening trapezoidal compartments, the outer edges of said horizontal top closures extending laterally into abbuting relationship with the pan side walls so as to provide completely sealed top closures for said downwardly opening compartments when said pan is filled with water to the level of said 9 tep closures and subjected to freezing tempera ure.

2. In combination, an elongated freezing pan and a closely fitting molded plastic grid removably positioned therein to form with the pan a series of ice block compartments, said grid comprising: a continuous longitudinal vertical main wall serving as a backbone for the grid to stiffen the grid against vertical bending, a continuous wall integral with and projecting laterally from each side of said longitudinal wall and shaped to form a series of alternately upwardly and downwardly opening trapezoidal shaped ice block compartments along the length of said longitudinal wall, said continuous walls forming horizontal top .closures for the downwardly opening compartments and horizontal bottom walls for the upwardly opening compartments, said continuous walls extending laterally and having free outer edges substantially abutting the pan side walls and so arranged that said outer edges .will be sealed to the pan side walls by the freezing of a relatively thin layer of ice on the inside surface of the pan side walls when said pan is fllled with water to the level of said top closures and sub- 7 jected to freezing temperature, whereby unfrozen water is trapped within the downwardly opening compartments and upon subsequent freezing will apply its force of expansion directly against said top closures to lift the grid relative to the pan.

FREDERICK W. SAMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,738,162 Weeks Dec. 3, 1929 2,028,047 Cole Jan. 14, 1936 2,265,349 Cole Dec. 9, 1941 2,386,979 Rundell Oct. 16, 1945 FOREIGN PATENTS Number Country Date 455,011 Great Britain Oct. '12. 1936 

